Undernutrition: Undernutrition occurs when the body doesn't receive enough calories or essential nutrients. Examples include children who do not receive enough food and suffer from stunted growth or individuals with a lack of iron leading to anemia.

Overnutrition: Overnutrition is when a person consumes an excess of calories or specific nutrients. Common examples include overeating leading to obesity and consuming too much sugar or unhealthy fats, which can lead to conditions like diabetes and heart disease.